1. Field of the Invention
The present invention relates to a device for covering an oblong opening in a housing, wherein an element extending with a portion of itself into the housing is movable back and forth, along the opening. The device comprises a flexible band connected with the element, and the width of the band is greater than the width of the opening in the housing. The band is held on the housing at the ends of the opening.
2. Brief Description of the Prior Art
In a known device (German Utility Model No. 82 34 393) for covering the surface of a machine bed, a band comprising two sections is provided, and one end of each section of the band is immovably secured to the carriage that is movable over the machine bed. The other end area of each section of the band is wound onto a roller, provided on the end of the machine bed. Since the band is of spring steel which has been deformed appropriately beforehand, a winding up of the band onto the roller at either end is effected automatically; that is, as the carriage moves relative to the machine bed, one section of the band is pulled off its roller and the other section is wound onto its roller.
This known device requires either a band with particular self-winding spring characteristics or, if such a band is not desired, then resilient clamping devices are needed to cooperate with the rollers, in order to wind up the respective band sections onto the roller and keep them taut. The capacity of such a device to function becomes impaired, should the spring action decrease as a result of material fatigue or the like.
A device is also known (German published application DE-OS No. 22 65 080) in which a machine bed and a belt-driven carriage are enclosed by a casing, in which there is a slit through which a tool carrier extends. A belt, which acts as the carriage drive means, extends on the inside of the slit and is used as a covering means. The belt further is guided over two rollers, provided at the ends of the slit; an upper segment acting as the slit covering, and a lower segment. However, this approach makes a relatively large belt dimension necessary. Furthermore, it must be assured that the upper segment of the belt is always taut; that is, it must be prevented from becoming slack, because of stretching or fatigue of the material caused by the continual movement of the belt back and forth, and thereby becoming spaced apart from the slit.